This application claims the priority of German application 197 33 476.8, filed Aug. 2, 1997, the disclosure of which is expressly incorporated by reference herein.
The present invention concerns a process for producing an assembly linkage or connection on a hollow profile which is shaped for attachment of an assembly part by internal high-pressure processes, and an apparatus for carrying out the process.
DE 41 03 083 C1 describes a metal pipe junction which is produced by internal high-pressure forming or remodeling. Partly circular cylindrical protrusions with plane assembly surfaces are shaped simultaneously for each air/fuel ratio detector. Such protruding assembly surfaces, as a consequence of internal high-pressure remodeling, are shaped exactly in the correct position for the respective purpose; however, they require additional space for components which is undesirable in tight assembly spaces. In addition, while precisely calibrated assembly surfaces can be produced on the assembly part, the specifically shaped remodeling or forming tool for this process is very costly in its production and because of its configuration limited to a very specific kind of assembly surface. Thus, such tool is essentially completely useless for producing differently shaped assembly surfaces. Moreover, the production of assembly surfaces, which require high degrees of remodeling of hollow profile, is not possible in a safe manner, as the pure widening soon surpasses the expandability of the hollow profile, whereupon the hollow profile then bursts.
An object of the present invention is to further improve a process and also an apparatus so that, for shaping of a component part, space-saving, for the subsequent assembly correctly placed, and, also with regard to the contour of the assembly part, an exactly fitted assembly connection is achieved simply and safely, even with the requirement of high degrees of forming or remodeling.
In accordance with the present invention, this object has been achieved by providing that the hollow profile at an internal pressure, which is lower than the remodeling pressure, is indented by a die at the point of the to-be-manufactured assembly linkage, causing the formation of a rough contour of the assembly connection or linkage, so that afterward when the die remains in the position where it has created the indent, a fluid internal high pressure is created in the hollow profile with which the hollow profile sides, surrounding the external contour of the die, are pressed into the die, and that after the relieving of the fluid pressure and subsequent removal of the die, the manufactured trough-shaped assembly linkage is released.
In addition, the process is effected by a novel apparatus in which the notch is shaped in the form of a bore into which a die is guided, which is controlled in such a manner that, with inserted hollow profile, it can be driven into the engraving for the purpose of indenting the hollow profile at pressure conditions below the remodeling pressure and prior to the internal high-pressure remodeling pressure, and afterwards retracted from the engraving, and during the remodeling process of the hollow profile, against the remodeling pressure, it remains backstopped in its indenting position.
The present invention advantageously provides a linkage or connection for the assembly set into the hollow profile, thereby eliminating the requirements for additional space for components for fitting into one another the hollow profiles and an assembly part. Thus, the assembly can be completed in an extremely component part, space-saving manner. Because of the internal high-pressure remodeling or forming process, the linkage or connecting point on the hollow profile is formed without tolerances with regard to its relative position, and in the contour fitted in an advantageous manner through a corresponding shaping of the die in joint application with internal high pressure, as it were, in an inverted shape to the connecting point of the assembly part. Thereby, a secure, durable fitting connection is achieved between the hollow profile and the assembly part, in which an optimal form fit is attained and with it an exact fitting into one another of the two assembly pieces, the hollow profile and the assembly part.
By using a die for the shaping of the connecting or linkage point, the apparatus becomes significantly more flexible, because, through the simple substitution of the die manifold, connection points can be shaped without necessitating an entirely new tool. Also the simple substitution of the worn-out die through a new one is significantly more cost-effective than the refinishing of an entire tool, or even the replacement of a worn out tool by a new one. As a result of the present invention, linkage or connection points on the hollow profile with high degrees of forming or remodeling can be produced because, through the indenting step, a useful pre-shaping of the hollow profile is attained with which areas, which were originally further away from the connecting or linkage point before the indenting operation, are drawn in to this point so that there is enough material left over for the final shaping by internal high pressure.
Moreover, the thus-obtained additional material has been pushed in the direction of the center of the hollow profile even before the internal high-pressure impingement. Thereby, the die, by indenting of the hollow profile side alone, is fully surrounded by a rough shape which approaches the final shape of the assembly linkage. The internal high pressure then is only responsible for establishing the final contact of the hollow profile material with the die that remains in this indenting position. For this, however, only small remodeling or forming degrees are required, whereby a complete failure of the hollow profile in the form of bursting is avoided. Thus, the present invention results in a process through which the production of such an assembly linkage sunk into the hollow profile can take place safely and simply.